There are three I'm considering: ITTT, i to i, and ICAL...has anyone had any experience with these by chance? And would choosing the course that offers the most hours (within the same price range) be a deciding factor? I'm also interested to know how these or other providers follow up on their job placement support.

Online courses are not generally looked on favorably by employers. A 30-day on-site course with supervised teaching practice is usually the minimum. This may not apply to you if you have other credentials in the field, like education/English degrees/advanced degrees/tons of previous experience. But if you're just wishing to enter the field now with a minimum investment, you need to check with employers in the area where you want to work, and find out what training they will accept.

thanks for your response. I lived and worked as a teacher (private mostly) in Italy, and had friends who'd recieved online certificates and found jobs where i was a bit locked out for lack of one. Hence my interest in this, and that i can't afford the 4 week intensive.

Obviously, the on-line qualification will be better than nothing, and with previous experience, and hopefully recommendations, you should be relatively ok....
Sorry, I can't recommend any on-line program over others, but good luck in any case.